German Laid-Open Specification DE 199 01 789 A1 discloses a method for determining the direction of ground faults in a section of a magnetic levitation transport system. The magnetic levitation transport system is formed by an electrical radial network which has a section cable to which a number of outgoers can be connected. Each of the outgoers is connected at one end of a linear stator, which is in each case associated with a specific section of the magnetic levitation transport system. In order to activate a specific section of the magnetic levitation transport system, the appropriate outgoer is connected to the section cable via a switching point. The other end of the linear stator is connected to a reference potential. When a ground fault occurs, the ground fault direction is determined at the switching point for the outgoer that has been monitored by detecting the zero voltage which results from the phase voltages that are applied to that outgoer and, in a corresponding manner, by detecting the resultant zero current on the basis of the phase currents. The ground fault direction is determined on the basis of the zero voltage and of the zero current, with a fault direction signal being formed. Therefore, it is possible to decide whether the ground fault that has been found is on the outgoer that is being monitored (forward direction) or is not (backward direction). The method is in each case carried out separately for each of the outgoers, in order to monitor all the sections of the magnetic levitation transport system. The method is particularly suitable for variable-frequency operating voltages, such as those which occur, for example, during operation of magnetic levitation transport systems.
European Laid-Open Specification EP 0 554 553 A2 discloses a method and a system for disconnection of a faulty section of a power supply network. This document describes a power supply line which is connected to a substation and has a number of line sections which are connected in series via switches. An outgoer branches off from one of the line sections, and is likewise subdivided into two outgoer line sections, via a switch. Each of the switches has an associated so-called controller, by which the associated switch can be operated. The substation has an associated so-called main controller, which is connected to each of the controllers for data transmission. When a fault occurs in the power supply network, such a fault is first detected in the substation. This sends a stimulus signal to the main controller. The main controller then sends a fault determination request signal to all the controllers. In response to this fault determination request signal, each controller determines whether the fault is on the load side of the switch associated with it. In this case, each controller produces a result signal, which includes one of the two events YES=load-side fault or NO=not a load-side fault. Each controller then sends its result signal to every other controller and to the main controller. The result signals from all the controllers are thus available in each of the controllers. Each controller now uses the result signals autonomously to determine whether the switch associated with it is the one which is physically closest to the fault on the substation side. If this is the case, then the relevant controller autonomously trips the switch associated with it, so that the faulty part of the power supply network is disconnected. The main controller uses the result signals to which it has access to determine the faulty section, and passes the result to a display unit for display, or outputs the result to a printer.